I’ve seen a few cases of this now in the wild within my organisation, where previously activated Windows 7 devices would suddenly report that they were no longer activated. On running “slmgr /dlv” I could see that the client reported as unlicenced, with the notification reason as “0xc004f200 (non-genuine)“

Don’t forget the Windows 7 key in my example above is for Windows 7 Enterprise, grab the right key for your edition of Windows 7 from Microsoft’s KMS Keys Page.This should remove the offending update and re-activate the copy of Windows against your KMS server.

UPDATEMicrosoft have confirmed that the Windows activation problem is in fact unrelated to the January 2019 update, and is in fact caused by a separate update to Microsoft Activation and Validation and has since been rerverted by them